A massive container ship lost power early Tuesday before crashing into the Francis Scott Key Bridge in Baltimore, causing it to collapse into the frigid Patapsco River along with people and vehicles, officials said.

At least six people believed to be part of a construction crew repairing potholes on the bridge remain unaccounted for, Maryland Transportation Secretary Paul J. Wiedefeld said at a news conference Tuesday.

Two people were pulled from the Patapsco River, Baltimore City Fire Department Chief James Wallace said. One was not injured and the other was taken to a local trauma center in “very serious condition,” he said. A patient being treated at the University of Maryland Medical Center was discharged later Tuesday, the hospital said in a statement.

Baltimore City Council Member Phylicia Porter told CNN’s Boris Sanchez on Tuesday afternoon a body had been recovered from the river, but later said she misspoke.

The crew of the ship notified officials that it had lost power prior to the crash, Maryland Gov. Wes Moore said, noting the warning likely saved lives.

“We’re thankful that between the mayday and the collapse, that we had officials who were able to begin to stop the flow of traffic so more cars were not on the bridge,” Moore said. He called those officials heroes.

Moore noted that the bridge was up to code at the time of the collapse. He said the collapse was a “shocking and heartbreaking” event for the people of Maryland who have used the bridge for 47 years.

The Democratic governor told reporters later Tuesday there was no more information to share, other than the search continues for the six people that remain missing.

Several vehicles are believed to have fallen into the water, including one as large as a tractor-trailer, Kevin Cartwright, director of communications of the Baltimore City Fire Department said early Tuesday.

Search and rescue crews used infrared and sonar technology to “mark” five vehicles under water in the Patapsco River, three of which are believed to be passenger vehicles, Wallace told CNN on Tuesday. There are eight dive teams made up of about 50 divers, working on the rescue effort, he added.

There are no known victims in the water who were in vehicles on the bridge at the time of the accident, Wiedefeld said.

“We have an unspeakable tragedy,” Baltimore Mayor Brandon Scott told CNN.

“There were individuals working on the bridge at the time. There are cars in the water – our fire department has confirmed that as they lead this search-and-rescue mission through sonar. That is where our focus is – it’s about those souls, those people we’re trying to find and get out of this water,” Scott said.

Construction workers contracted with the state transportation agency were doing repair work on the bridge at the time of the collapse, Wiedefeld said Tuesday morning. He did not specify how many workers were there.

The ship, which hit the bridge just before 1:30 a.m., was the DALI, a Singaporean-flagged container vessel, Coast Guard spokesperson Kimberly Reaves said. It’s about 984-feet long and 157-feet wide, Synergy Group spokesman Pat Adamson told CNN. It was leaving Baltimore when it crashed, according to the company website.

Previously, the US Coast Guard reported it was a 948-foot container ship.

The ship dropped its anchors as part of an emergency procedure before hitting the bridge, the Maritime and Port Authority of Singapore told CNN. The vessel is currently holding its position at the site of the collision and is in a stable condition and all 22 of the ship’s crew members are safe and accounted for, the agency added.

Lights on the ship flickered and a dark plume of smoke could be seen billowing from it before it veered towards a bridge pillar shortly before impact, CNN analysis of data from MarineTraffic shows.

No crew members on the ship were injured, ship management company Synergy Group said a statement.

Multiple agencies are investigating the crash, though there is currently “absolutely no indication that it was intentional,” Baltimore Police Commissioner Richard Worley said Tuesday morning.

National Transportation Safety Board Chair Jennifer Homendy told reporters Tuesday afternoon her federal agency would be leading the investigation into the crash and collapse with the help of the Coast Guard.

Homendy added a team of 24 — including experts in nautical operations, human performance and engineering — will begin looking into the incident and collect information on the vessel, including obtaining recorders on the ship. But for the moment, she said, “we are standing back to allow the Coast Guard and search and rescue to continue search and rescue operations while we gather information from the command post.”

She did not provide updates on fatalities, the nationality of the crew or the structural integrity of the bridge.

“The NTSB doesn’t speculate, we provide facts,” Homendy said. “So there isn’t a lot we can share right now because the focus has been on the people.”

At the afternoon news conference, the governor thanked first responders for their continued search and rescue efforts and President Joe Biden and Vice President Kamala Harris for their “full-throated” support. Moore also thanked US Transportation Secretary Pete Buttigieg — who he said called him around 3:30 a.m. Tuesday to offer help — and Maryland’s congressional delegation.

Buttigieg also addressed reporters, noting the road to recovery and rebuilding will “not be quick” and will certainly be costly. “But we will rebuild,” he said. He also looked to ease fears about bridge safety across the country, calling the Key Bridge collapse “a unique circumstance.”

“I do not know of a bridge that has been constructed to withstand a direct impact from a vessel of this size,” he said.

The 1.6-mile, four-lane bridge extends over the Patapsco River and serves as the outermost crossing of the Baltimore harbor and an essential link of I-695, or the Baltimore Beltway.

“There is no question that this will be a major and protracted impact to supply chains. It’s too soon to offer estimates on what it will take to clear the channel and reopen the port,” Buttigieg said.